Multi-Split Air Conditioning System and Control Method Therefor

ABSTRACT

The present disclosure discloses a control method for a multi-split air conditioning system and a multi-split air-conditioning system, the multi-split air conditioning system, including a compressor and a plurality of indoor units respectively arranged on a plurality of parallel branches, the indoor unit including a fan and the control method including: in a cooling mode, when the multi-split air conditioning system needs oil return, the multi-split air conditioning system opening a branch where an indoor unit in an off state is located, determining whether the indoor unit has reached a dewing condition, opening the branch on which the indoor unit is located, and controlling the fan of the indoor unit according to a determination result.

TECHNICAL FIELD

The present invention relates to the technical field of an airconditioner, in particular to a control method for a multi-split airconditioning system and a multi-split air conditioning system controlledusing the control method.

BACKGROUND

In an air-conditioning system, after a compressor is operated for aperiod of time, a refrigeration oil may be circulated in the systemalong with a refrigerant, which causes the refrigeration oil to possiblyremain in an indoor heat exchanger or in a pipe between an indoor unitand an outdoor unit. If such refrigeration oil cannot return to theoutdoor unit in time, the compressor cannot be effectively lubricatedand cooled by the refrigeration oil, thereby affecting the operatingperformance and reliability of the compressor. Therefore, after theair-conditioning system is operated for a period of time, it isnecessary to perform oil return to bring the refrigeration oil broughtout by the compressor during exhaust of the compressor back into thecompressor, thereby ensuring normal operation of the air-conditioningsystem. In a multi-split air conditioning system comprising multipleindoor units, when the compressor returns oil, an electronic expansionvalve of the indoor unit in an off state needs to be turned on in orderto return the refrigeration oil to the outdoor unit. When themulti-split air conditioning system is operated in a cooling mode, ifthe compressor frequently returns oil, a problem of dewing and drippingwill occur at the indoor unit in an off state for a long time, whichwill affect the user's experience.

SUMMARY

In view of this, one of the objectives of the present invention is toprovide a control method for a multi-split air conditioning system and amulti-split air conditioning system which is controlled using thecontrol method, which are capable of effectively solving the problem ofdewing and dripping at the indoor unit resulting from frequent oilreturn of the compressor, and improving the user's operational comfort.

To achieve the above-described objective, on the one hand, the presentinvention uses the following technical solution: a control method for amulti-split air conditioning system, wherein the multi-split airconditioning system comprises a compressor and a plurality of indoorunits respectively disposed on a plurality of parallel branches, each ofthe plurality of indoor units comprises a fan, and the control methodcomprises: in a cooling mode, when the multi-split air conditioningsystem needs oil return, the multi-split air conditioning systemdetermining whether an indoor unit in an off state reaches a dewingcondition, opening a branch where the indoor unit is located, andcontrolling the fan of the indoor unit differently according to adetermination result.

Optionally, the control method further comprises: when it is determinedthat the indoor unit in the off state does not reach the dewingcondition, controlling the fan of the indoor unit to maintain an offstate during the oil return of the multi-split air conditioning system;and/or, when it is determined that the indoor unit in the off statereaches the dewing condition, controlling the fan of the indoor unit tobe turned on during the oil return of the multi-split air conditioningsystem.

Optionally, each of the plurality of indoor units further comprises athrottling device, and a way to open the branch where the indoor unit islocated is to open the throttling device of the indoor unit.

Optionally, the throttle device is opened at an opening degree of 30% to60%.

Optionally, when it is determined that the indoor unit in the off statereaches the dewing condition, the fan of the indoor unit is controlledto be operated at a low grade speed during the oil return of themulti-split air conditioning system.

Optionally, the dewing condition comprises: a current humidity of anenvironment where the indoor unit is located being higher than ahumidity threshold.

Optionally, the humidity threshold is 60% to 80%.

Optionally, it is determined whether the indoor unit in the off statereaches the dewing condition at least according to a frequency of oilreturn of the multi-split air conditioning system.

Optionally, the dewing condition comprises: the frequency of oil returnof the multi-split air conditioning system reaching or being higher thana predetermined frequency.

Optionally, the predetermined frequency is one oil return every 0.5 to 2hours.

Optionally, the dewing condition further comprises: the fan of theindoor unit being not effectively operated during a time period betweenan end of the previous oil return and a beginning of the present oilreturn.

Optionally, a criteria for determining an effective operation of the fancomprises: whether the fan being turned on at least once.

Optionally, the criteria for determining the effective operation of thefan further comprises: whether a continuous operation time of the fanexceeding a predetermined time.

Optionally, the predetermined time is 5 to 15 minutes.

On the other hand, the present invention uses the following technicalsolution: a control method for a multi-split air conditioning system,wherein the multi-split air conditioning system comprises a compressorand a plurality of indoor units respectively disposed on a plurality ofparallel branches, each of the plurality of indoor units comprises afan, and the control method comprises: in a cooling mode, during oilreturn of the multi-split air conditioning system, the multi-split airconditioning system controlling a branch where an indoor unit in an offstate is located to be opened, and turning on the fan of the indoorunit.

Optionally, in the cooling mode, the multi-split air conditioning systemcontrols the fan to be operated at a low grade speed during the oilreturn of the multi-split air conditioning system.

In a further aspect, the present invention uses the following technicalsolution: a multi-split air conditioning system which is controlledusing the control method described above.

In the control method for the multi-split air conditioning systemprovided by the present invention, when the compressor needs oil return,first of all, it is determined whether there is a risk of dewing in theindoor unit in an off state, and different control methods are used forthe fan according to different conditions, so as to solve the problem ofdewing and dripping at the indoor unit resulting from frequent oilreturn of the compressor, and improve the user's operational comfort.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described and other objectives, features, and advantages ofthe present invention will be more apparent from the followingdescription of embodiments of the present invention in conjunction withthe accompanying drawings, in which:

FIG. 1 is a schematic structural view of a multi-split air conditioningsystem provided by the present invention;

FIG. 2 shows a flow chart of a control method when an existingmulti-split air conditioning system returns oil;

FIG. 3 shows a flow chart of a control method of an embodiment for themulti-split air conditioning system provided by the present invention;

FIG. 4 shows a flow chart of a control method of another embodiment forthe multi-split air conditioning system provided by the presentinvention.

In the figures, 1, an outdoor unit; 2, an indoor unit; 21, an electronicexpansion valve; 22, a fan; 23, an indoor heat exchanger.

DETAILED DESCRIPTION

The present invention is described below based on the embodiments, butthe present invention is not only limited to these embodiments. In thefollowing detailed description of the present invention, some specificdetails are expatiated. For those skilled in the art, the presentinvention may also be fully understood without the description of thesedetails. In order to avoid obscuring the essence of the presentinvention, well-known methods, processes, procedures, and elements arenot described in detail.

In addition, those skilled in the art should understand that thedrawings provided here are for the purpose of illustration, and thedrawings are not necessarily drawn to scale.

Unless specifically required in the context, the words “comprising”,“including”, and the like throughout the specification and claims shouldbe interpreted as inclusive rather than exclusive or exhaustive, thatis, the meaning of “comprising but not limited to”.

In the description of the present invention, it should be understoodthat, the terms “first”, “second”, and the like are used for descriptivepurposes only, and cannot be understood to indicate or imply relativeimportance. In addition, in the description of the present invention,unless otherwise stated, the meaning of “a plurality of” is two or more.

For the problem that the indoor unit in an off state for a long time maysuffer from dewing and dripping caused by frequent oil return of thecompressor present in the existing multi-split air conditioning system,it is found in the present application that it is caused due to thereasons that the existing oil return control method is not reasonable.Specifically, as shown in FIG. 1, the multi-split air conditioningsystem comprises an outdoor unit 1 and a plurality of indoor units 2arranged in parallel. That is, a plurality of parallel branches areprovided on the refrigerant circulation circuit, and different indoorunits 2 are respectively provided on different branches to realizemutual parallel connection of the indoor units 2. The outdoor unit 1 isinternally provided with a compressor, and the indoor unit 2 comprises athrottling device, an indoor heat exchanger 23, and a fan 22. Thethrottling device may be any device capable of throttling therefrigerant, and an electronic expansion valve 21 shown in FIG. 1 ispreferably used as the throttling device to facilitate automaticcontrol. The fan 22 is provided to drive air flow to promote heatexchange between the air and the indoor heat exchanger 23. The existingcontrol method is shown in FIG. 2. The multi-split air conditioningsystem is operated in a cooling mode. When the multi-split airconditioning system needs oil return, the operational state of theindoor unit 2 is determined. The fan 22 and the electronic expansionvalve 21 of the indoor unit 2 in an operational state remain in an onstate. Whereas, the indoor unit 2 in an off state controls the branchwhere the indoor unit 2 is located to be opened. For example, theelectronic expansion valve 21 of the indoor unit 2 may be turned on; ora solenoid valve may also be provided on the branch, and the branchwhere the indoor unit 2 is located is opened by controlling the solenoidvalve, so that the refrigerant and the refrigeration oil may becirculated, and the fan 22 always maintains an off state. For the indoorunit 2 in the off state, during oil return of the system, since the fan22 is in an off state, the low-temperature and low-pressure refrigerantcannot be effectively evaporated in the indoor heat exchanger 23thereof, and the low-temperature and low-pressure refrigerant may remainin the indoor heat exchanger 23 after completion of the oil return,which results in outward transmission or radiation of the cold quantity. When the system frequently returns oil, the dewing and drippingphenomenon may occur at the indoor unit 2 in the off state for a longtime.

In view of the above problem, the present application provides a controlmethod for a multi-split air conditioning system. In a cooling mode,when the compressor needs oil return, the multi-split air conditioningsystem determines whether the indoor unit 2 in an off state reaches adewing condition. That is, it is determined whether there is a dewingrisk in the indoor unit 2 in the off state. And different controlmethods are used according to different conditions, so as to solve theproblem of dewing and dripping at the indoor unit 2 resulting fromfrequent oil return of the compressor, and improve the user'soperational comfort.

Wherein, if it is determined that the indoor unit 2 in the off statedoes not reach the dewing condition, which means that the indoor unit 2does not have the dewing risk, the oil return control of the indoor unit2 is performed according to a conventional control method. That is,during the oil return of the multi-split air conditioning system, theelectronic expansion valve 21 of the indoor unit 2 is controlled to beturned on until the oil return process ends, and the fan 22 alwaysmaintains an off state. If it is determined that the indoor unit 2 inthe off state reaches the dewing condition, which means that the indoorunit 2 has the dewing risk, at this time, it is necessary to control theoil return of the indoor unit 2 by using an improved control method soas to avoid the problem of dewing and dripping on the indoor unit 2.Specifically, during the oil return of the multi-split air conditioningsystem, the electronic expansion valve 21 and the fan 22 of the indoorunit 2 are both controlled to be turned on until the oil return processends, so that during the oil return, the evaporation of the refrigerantwithin the indoor heat exchanger 23 of the indoor unit 2 is promoted bythe fan 22, so as to achieve the effect of avoiding dewing. Preferably,in order to reduce the impact caused by the operation of the fan 22 overthe environment of the area where the fan 22 is located, the fan 22 ofthe indoor unit 2 is controlled to be operated at a low-grade speedduring the oil return of the multi-split air conditioning system. Thelow-grade speed described herein may be, for example, the lowest gradespeed or the silent grade speed of the indoor unit.

There may be multiple methods for determining whether the indoor unit 2in the off state reaches the dewing condition. For example, in anembodiment, a humidity sensor is provided in the indoor unit 2 to detecta humidity of the environment in which it is located, and it determineswhether the indoor unit 2 has the dewing risk according to the humidityof the environment where the indoor unit 2 is located. That is, thedewing condition comprises: the humidity of the environment where theindoor unit 2 is located being higher than a humidity threshold. If theenvironment where the indoor unit 2 is located has a low humidity, it isindicated that there is a low air humidity without the dewing risk. Ifthe environment where the indoor unit 2 is located has a high humidity,it is indicated that there is a high air humidity. If the fan 22 is notturned on, the water vapor in the air during the oil return may condenseto produce a dewing. Preferably, the humidity detected by the humiditysensor provided in the indoor unit 2 is used as the humidity of theenvironment where the indoor unit 2 is located. Specifically, thehumidity of the environment where the indoor unit 2 is located isobtained, and whether the humidity of the environment where the indoorunit 2 is located is higher than a humidity threshold is determined. Ifso, it is determined that the indoor unit 2 reaches the dewingcondition. Otherwise, it is determined that the indoor unit 2 does notreached the dewing condition. The humidity threshold therein preferablyranges 60% to 80%.

As shown in FIG. 3, the method of controlling the oil return in acooling mode by using the above-described determination mannercomprises:

At step S001, when the multi-split air conditioning system needs oilreturn, whether the indoor unit 2 is in an operational state isdetermined. If so, proceed to step S005, otherwise proceed to step S002.

At step S002, the current humidity of the environment where the indoorunit 2 in an off state is located is obtained, and whether the currenthumidity is higher than a humidity threshold is determined. If so,proceed to step S003, otherwise proceed to step S004.

At step S003, the electronic expansion valve 21 and the fan 22 of theindoor unit 2 are both turned on, the fan 22 is operated at a low-gradespeed, and the electronic expansion valve 21 and the fan 22 are turnedoff after completion of the oil return.

At step S004, the electronic expansion valve 21 of the indoor unit 2 isturned on, and the electronic expansion valve 21 is turned off aftercompletion of the oil return, while the fan 22 is always in an offstate.

At step S005, the operational state of the indoor unit 2 remainsunchanged, and the electronic expansion valve 21 and the fan 22 maintainan on state.

In another embodiment, since the dewing phenomenon is caused by frequentoil return of the multi-split air conditioning system, based on this, itmay be determined whether the indoor unit 2 in the off state reaches thedewing condition according to a frequency of oil return of themulti-split air conditioning system. That is, the dewing conditioncomprises: the frequency of oil return of the multi-split airconditioning system reaching or being higher than a predeterminedfrequency. When the frequency of oil return of the multi-split airconditioning system reaches or is higher than the predeterminedfrequency, there is a risk of accumulating excessive low-temperature andlow-pressure refrigerant in the indoor heat exchanger 23 of the indoorunit 2 in the off state. If excessive low-temperature and low-pressurerefrigerant is accumulated, it will also emit more cold quantity, and atthis time, there is a dewing risk. When there is a low frequency of oilreturn of the multi-split air conditioning system, it is indicated thatthe cold quantity of the low-temperature and low-pressure refrigerantaccumulated in the indoor heat exchanger 23 of the indoor unit 2 in theoff state is not enough to cause the dewing phenomenon. Thepredetermined frequency may be set according to a specific model andapplication scenario. The preferred range of the predetermined frequencyis one oil return every 0.5 to 2 hours. For example, the predeterminedfrequency is one oil return every 0.5 hours, two oil returns every twohours, or three oil returns every three hours. In a preferredembodiment, the predetermined frequency is four oil returns every 8hours.

In a further preferred control method, the dewing condition may furthercomprise: the fan 22 of the indoor unit 2 in the off state being noteffectively operated during a time period between an end of a previousoil return and a beginning of a present oil return. That is, in the casewhere the multi-split air conditioning system frequently returns oil, ifthe indoor unit 2 currently in the off state has been operated before,there may not be excessive low-temperature and low-pressure refrigerantaccumulated in the indoor heat exchanger 23 of the indoor unit 2, andthus there is no dewing risk. If the indoor unit 2 in the off state hasnot been operated before, at this time, there may be muchlow-temperature and low-pressure refrigerant accumulated in the indoorheat exchanger 23 of the indoor unit 2, and thus there may be the dewingrisk.

Optionally, a criteria for determining an effective operation of the fan22 comprises whether the fan 22 being turned on at least once. If so, itis determined that the fan 22 has been operated effectively, otherwiseit is determined that the fan 22 has not been operated effectively.Since there is a little effect on the refrigerant in the indoor heatexchanger 23 when the fan 22 has been turned on for a short time, inorder to improve the accuracy of the determination, further preferably,the criteria for determining the effective operation of the fan 22further comprises whether a continuous operation time of the fan 22exceeding a predetermined time. If so, it is determined that the fan 22has been operated effectively, otherwise it is determined that the fan22 has not been operated effectively. The predetermined time therein maybe set according to specific conditions. Preferably, the predeterminedtime ranges from 5 to 15 minutes, and may be, for example, 5 minutes, 10minutes, 15 minutes, and further preferably 10 minutes.

As shown in FIG. 4, the method of controlling the oil return in acooling mode by using the above-described determination mannercomprises:

At step S010, when the multi-split air conditioning system needs oilreturn, whether the indoor unit 2 is in an operational state isdetermined. If so, proceed to step S060, otherwise proceed to step S020.

At step S020, whether the frequency of oil return of the multi-split airconditioning system reaches or is higher than the predeterminedfrequency is determined. If so, proceed to step S030, otherwise proceedto step S040.

At step S030, whether the fan 22 of the indoor unit 2 in an off statehas been effectively operated is determined during a time period betweenthe end of the previous oil return and the beginning of the present oilreturn. If so, proceed to step S040, otherwise proceed to step S050.

At step S040, the electronic expansion valve 21 of the indoor unit 2 isturned on, and the electronic expansion valve 21 is turned off aftercompletion of the oil return, while the fan 22 is always in an offstate.

At step S050, the electronic expansion valve 21 and the fan 22 of theindoor unit 2 are both turned on, the fan 22 is operated at a low-gradespeed, and the electronic expansion valve 21 and the fan 22 are turnedoff after completion of the oil return.

At step S060, the operational state of the indoor unit 2 remainsunchanged, and the electronic expansion valve 21 and the fan 22 maintainan on state.

It maybe understood that, when the electronic expansion valve 21 isturned on, the opening degree of the electronic expansion valve 21 maybe set according to an actual refrigerant condition. For example, theopening degree of the electronic expansion valve 21 when turned on iscontrolled to be within a range of 30% to 60%.

In an alternative embodiment, it is also possible not to determinewhether the dewing condition is reached. For example, in certainapplication scenarios, the indoor unit is always in a state having ahigh dewing risk. At this time, it is not necessary to determine whetherthe dewing condition is reached. In a cooling mode, as long as themulti-split air conditioning system returns oil, the electronicexpansion valve 21 and the fan 22 of the indoor unit 2 in an off stateare controlled to be turned on. Preferably, the fan 22 is controlled tobe operated at the lowest speed, so that it is also possible to achievethe effect of avoiding the dewing and dripping phenomenon of the indoorunit 2 in the off state.

Those skilled in the art may easily understand that, under the premisethat there is no conflict, various preferred solutions as describedabove may be freely combined and superimposed.

It should be understood that, the above-described embodiments are merelyexemplary but not restrictive, and those skilled in the art may makevarious obvious or equivalent modifications or replacements directed tothe above-described details without departing from the basic principlesof the present invention, which will be all comprised in the scope ofthe claims of the present invention.

INDUSTRIAL APPLICABILITY

The solution provided by embodiments of the present invention may beapplied to a control process of the multi-split air conditioning system.The multi-split air conditioning system comprises a compressor and aplurality of indoor units respectively disposed on a plurality ofparallel branches. The indoor unit comprises a fan. The control methodcomprises: in a cooling mode, when the multi-split air conditioningsystem needs oil return, the multi-split air conditioning systemdetermining whether an indoor unit in an off state reaches a dewingcondition, opening a branch where the indoor unit is located, andcontrolling the fan of the indoor unit differently according to adetermination result. In the control method for the multi-split airconditioning system provided by the present invention, when thecompressor needs oil return, first of all, it is determined whetherthere is a dewing risk in the indoor unit in an off state, and differentcontrol methods are used for the fan according to different conditions,so as to solve the problem of dewing and dripping at the indoor unitresulting from frequent oil return of the compressor, and improve theuser's operational comfort.

1. A control method for a multi-split air conditioning system, whereinthe multi-split air conditioning system comprises a compressor and aplurality of indoor units respectively disposed on a plurality ofparallel branches, each of the plurality of indoor units comprises afan, and the control method comprises: in a cooling mode, when themulti-split air conditioning system needs oil return, the multi-splitair conditioning system opening a branch where an indoor unit in an offstate is located, determining whether the indoor unit reaches a dewingcondition, and controlling the fan of the indoor unit according to adetermination result.
 2. The control method according to claim 1,wherein the control method further comprises: when it is determined thatthe indoor unit in the off state does not reach the dewing condition,controlling the fan of the indoor unit to maintain an off state duringthe oil return of the multi-split air conditioning system; or, when itis determined that the indoor unit in the off state reaches the dewingcondition, controlling the fan of the indoor unit to be turned on duringthe oil return of the multi-split air conditioning system.
 3. Thecontrol method according to claim 2, wherein when it is determined thatthe indoor unit in the off state reaches the dewing condition, the fanof the indoor unit is controlled to be operated at a low-grade speedduring the oil return of the multi-split air conditioning system.
 4. Thecontrol method according to claim 1, wherein each of the plurality ofindoor units further comprises a throttling device, and a way to openthe branch where the indoor unit is located is to open the throttlingdevice of the indoor unit.
 5. The control method according to claim 4,wherein the throttle device is opened at an opening degree of 30% to60%.
 6. The control method according to claim 1, wherein the dewingcondition comprises: a current humidity of an environment where theindoor unit is located being higher than a humidity threshold.
 7. Thecontrol method according to claim 6, wherein the humidity threshold is60% to 80%.
 8. The control method according to claim 1, wherein it isdetermined whether the indoor unit in the off state reaches the dewingcondition at least according to a frequency of oil return of themulti-split air conditioning system.
 9. The control method according toclaim 8, wherein the dewing condition comprises: the frequency of oilreturn of the multi-split air conditioning system reaching or beinghigher than a predetermined frequency.
 10. The control method accordingto claim 9, wherein the predetermined frequency is one oil return every0.5 to 2 hours.
 11. The control method according to claim 9, wherein thedewing condition further comprises: the fan of the indoor unit being noteffectively operated during a time period between an end of a previousoil return and a beginning of a present oil return, and a criteria fordetermining an effective operation of the fan comprises: the fan beingturned on at least once.
 12. The control method according to claim 11,wherein the criteria for determining the effective operation of the fanfurther comprises: a continuous operation time of the fan exceeding apredetermined time.
 13. The control method according to claim 12,wherein the predetermined time is 5 to 15 minutes.
 14. A control methodfor a multi-split air conditioning system, wherein the multi-split airconditioning system comprises a compressor and a plurality of indoorunits respectively disposed on a plurality of parallel branches, each ofthe plurality of indoor units comprises a fan, and the control methodcomprises: in a cooling mode, during oil return of the multi-split airconditioning system, the multi-split air conditioning system controllinga branch where an indoor unit in an off state is located to be opened,and turning on the fan of the indoor unit.
 15. The control methodaccording to claim 14, wherein in the cooling mode, the multi-split airconditioning system controls the fan to be operated at a low-grade speedduring the oil return of the multi-split air conditioning system.
 16. Amulti-split air conditioning system, which is controlled using thecontrol method according to claim
 1. 17. The control method according toclaim 1, wherein the control method further comprises: when it isdetermined that the indoor unit in the off state does not reach thedewing condition, controlling the fan of the indoor unit to maintain anoff state during the oil return of the multi-split air conditioningsystem; and, when it is determined that the indoor unit in the off statereaches the dewing condition, controlling the fan of the indoor unit tobe turned on during the oil return of the multi-split air conditioningsystem.